Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
01-11-2010, 05:05 PM   #1
Junior Member




Join Date: Nov 2009
Location: mississippi
Posts: 38
How do a "test" a new lens for abnormalties?

Ive been seiing a lot of post about people buying new sigma lenses that were "soft" or "out of focus" at certain points ect. I am new to this and thinking about buying a sigma lense. How can a newbie like me "test" a lens when it arrives to see if its funcctioning properly?

01-11-2010, 05:16 PM   #2
Veteran Member




Join Date: Jan 2009
Location: Canada
Posts: 1,255
QuoteOriginally posted by dehanson1 Quote
Ive been seiing a lot of post about people buying new sigma lenses that were "soft" or "out of focus" at certain points ect. I am new to this and thinking about buying a sigma lense. How can a newbie like me "test" a lens when it arrives to see if its funcctioning properly?
Put your camera on a stable tripod and use the mirror lockup feature and preferably a shutter release cable. Turn off SR. Shoot under fluorescent light. Find a flat target, parallel to the sensor.
01-11-2010, 05:20 PM   #3
Senior Member




Join Date: Dec 2009
Location: United States
Posts: 112
1. grab a newspaper, lay it flat on a table

2. Set your camera's autofocus to the center point only. Turn the dial to Av mode and set the Aperture to the lowest number possible and zoom all the way in. You should probably use a tripod.

3. point the camera at a 45* angle to the newspaper

4. autofocus on a specific word in the newspaper - remember what word it was!

5. Now, do it again, but manually focusing the lens on the same spot.

6. Upload both shots to the computer to test

-Make sure the text you focused on in the first shot is the *most* in focus word. Words above and below it should be slightly out of focus.

-Compare 'sharpness' of the text that's in focus for both shots. Don't freak if the manually focused one is slightly sharper, it usually is
01-11-2010, 05:34 PM   #4
Pentaxian
Wheatfield's Avatar

Join Date: Apr 2008
Location: The wheatfields of Canada
Posts: 10,042
I just go out and take pictures.
I always find something to take a picture of that tests my camera's mettle.

01-11-2010, 05:36 PM   #5
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,312
I only do one real "test" before I go out and shoot

I check exposure at all F stops by shooting a block wall or paved roadway and then checking the average grey scale value. with neutral contrast, it shoudl be centered at about 110-120 and each F stop within a +/- 1.5 stop band has a range of about 45 greyscale around the 110-120 value

Then I go out and shoot. If I have issues with sharpness afterwards I might try focus tests but these are so badly designed they can be misleading. the best focus test is to focus on a flat wall at right angles and then blow this up for the detail, if it is sharp you don't have a focus issue
01-11-2010, 05:56 PM   #6
Veteran Member




Join Date: Jan 2009
Location: Canada
Posts: 1,255
QuoteOriginally posted by Wheatfield Quote
I just go out and take pictures.
I always find something to take a picture of that tests my camera's mettle.
Hmm...

http://www.youtube.com/watch?v=0toBw68L5Y4

01-11-2010, 05:58 PM   #7
Pentaxian
jimH's Avatar

Join Date: Apr 2009
Location: South Central Nebraska - USA
Photos: Gallery | Albums
Posts: 1,413
subscribe to this thread
01-11-2010, 06:45 PM   #8
Inactive Account




Join Date: Nov 2009
Posts: 14
QuoteOriginally posted by asdf Quote
.............Shoot under fluorescent light................
I do not understand why you would recommend this

01-11-2010, 06:49 PM   #9
Veteran Member




Join Date: Jan 2009
Location: Canada
Posts: 1,255
QuoteOriginally posted by 440roadrunner Quote
I do not understand why you would recommend this
Under tungsten light, *some* cameras consistently front focus with every lens.
01-11-2010, 07:08 PM   #10
Pentaxian
Wheatfield's Avatar

Join Date: Apr 2008
Location: The wheatfields of Canada
Posts: 10,042
QuoteOriginally posted by asdf Quote
HAR!!!!!!!!!
I went through that with the Zone System.
I could never get Tri-X to give me a perfect curve.
I hated Tri-X from the moment I bought a densitometer.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
camera, lens, pentax help, photography, sigma
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Do custom "artistic" or even "funny" lens caps evenexist? lovemehate Pentax SLR Lens Discussion 35 02-10-2016 09:10 AM
Which Zoom Lens? "Tamron AF 18-250mm", "Pentax-DA 18-250mm" or "Sigma 18-250mm" hoomanshb Pentax SLR Lens Discussion 4 07-30-2010 09:50 AM
K-mount Experts: How to convert a "KAF2" lens to "KF"? panoguy Pentax SLR Lens Discussion 24 07-08-2010 05:20 PM
Pentax "A" lens and "F" 1.7X converter on K10d yyyzzz Pentax SLR Lens Discussion 4 07-09-2009 05:04 AM
"Hunger for a DA*50-135?" or "The DA*50-135 as a bird lens!" or "Iron age birds?" Douglas_of_Sweden Post Your Photos! 4 08-13-2008 06:09 AM



All times are GMT -7. The time now is 03:22 PM. | See also: NikonForums.com, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top